60 Journal of the Department of Agriculture. 



The most striking features of this table are the very small 

 amounts of plant-food in the wine and the very large amounts in the 

 leaves. If it were practicable to return to the vineyard soil, the 

 leaves, shoots, and husks of the grapes, very little plant-food would 

 be lost from the soil, because these materials, when ploughed in, 

 would soon decay and yield their plant-food to the growing vines. 

 The coarser woody portions pruned off could even be burned and the 

 ash returned to the soil — the nitrogen would be burned off but the 

 phosphoric oxide and potash would remain in the ash. In the natural 

 course of events a portion of the plant-food in the leaves does ulti- 

 mately find its way back to the soil, but it is possible that this aspect 

 of the matter might with benefit receive more attention. However, 

 in ordinary farm practice, the vineyard undoubtedly loses a large 

 amount of plant-food annually. For this reason, and also because we 

 wish to increase the fertility of our naturally poor soils, and thereby 

 improve our vineyards in respect of both quantity and quality of 

 yield, manuring will alwaj^s be necessary. 



Taking the figures which indicate the plant-food removed by the 

 whole vineyard, we obtain an idea regarding the quantities of the 

 different plant-foods which should be returned to the soil, and it 

 would seem that the manure used should contain four to five times 

 as much of both nitrogen and potash as of phosphoric oxide. But 

 various other factors have to be taken into consideration, and these 

 will modify our decision in regard to the best type of fertilizer. 



As far as the plant-food content of the soil is concerned, in 

 general the soils of the south-west Cape, derived largely from rocks 

 of the Table Mountain series, Malmesbury series, and granite, are of 

 rather poor fertility. According to the 1918 Census, the most 

 important viticultural districts are Paarl, Worcester, Stellenbosch, 

 Robertson (including Montagu), and Malmesbury. In 1911 these 

 districts produced over 80 per cent, of the total crop of the Union 

 Among the larger producing districts, Worcester and Robertson have 

 soils of greater fertility than Paarl, Stellenbosch, Malmesbury, and 

 the Cape. However, with very few exceptions, the soils of all these 

 districts show a marked deficiency in phosphoric oxide, and the 

 supplies of nitrogen and potash are also low on the whole. In parts 

 of Robertson and Worcester areas there is abundance of lime in the 

 soils, but the soils of the other four districts mentioned are very 

 deficient in lime. 



With regard to the maintenance of fertility, it is necessary it 

 this point to make a distinction between vineyard lands on one hand 

 and grain lands on the other. In the case of grain farming we are 

 dealing with crops whose demands upon the plant-foods in the soil 

 are considerably smaller than those of the vine. A wheat crop giving 

 a return of 20 bags of grain per bag of seed (i.e. 8 bags per morgen") 

 will remove from the soil per morgen, approximately: — 



Nitrogen. Phosphoric Oxide. Potash. 



Grain (26 bushels) 36 lb. 14 lb. 8 lb. 



Straw m tons) 12 lb. 5 lb. 27 lb. 



Entire crop 48 lb. 19 lb. 35 lb. 



Moreover, we practise a rotation, and thus do not have the same 

 crop making the same demands year after year; and. usualh\ there 

 is a period of fallow in each rotation, when the soil has a rest. The 



